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What is the Best Protective Relay Test-Set?

Declaring the best protective relay test-set is a lot like declaring the best pickup truck. Any model of truck will get you from point A to point B in the city, but there are pros and cons for each one.  A smaller truck will be easier to park in the parking lot, but a larger truck has more power and can pull more stuff. A four-wheel drive will get you just about anywhere, but you’re paying for all those extra components and weight every time you drive it, even though you may only need it 5% of the time.  Then there are the little things like cruise control, wiper, radio, and signal light functions that will work for everyone, but can drive a GMC driver crazy when they jump into their Ford rental truck because everything is in the “wrong” place.

Relay testers spend a lot of time with their equipment, which can turn into an emotional attachment that is magnified by the time invested learning the software and building test plans. Asking a bunch of relay testers to recommend the “best” test-set is a loaded question that gets different answers from testers with different backgrounds.

A better question to ask is “What is the best protective relay test-set for me?”  Deciding on the best test-set for you should involve a little research, a demonstration from the protective relay test-set vendors, and a trial period where you can kick the tires to see if it fits your organization’s needs and relay testers’ temperaments.

This post discusses the pros and cons of the major test-sets sold in North America that I hope will help you make an informed decision. In the interest of full disclosure, I should mention that most of my career was spent behind the wheel of various test-sets from Manta Test Systems, and I used to represent Manta for a time. Valence Electrical Training Services is vendor-neutral and I’ve tried to be as fair as I can in this article, but I hope I didn’t tilt too far towards fairness.

We did not include some other test-sets sold in North America, because those test-sets may be able to supply similar currents on a single-phase or three-phase basis, but they can only supply 5A on the other side when six currents are required. Six currents are primarily used in differential relay testing, and five amps isn’t sufficient current to properly test a differential relay. It would not be fair to compare the full-spectrum test-sets on our list to a test-set that does not have the same functionality.

Protective Relay Test-Set Hardware

All of the modern test-sets with six current channels have the minimum requirements to test just about every digital relay.  If you plan on exclusively testing digital relays, you can skip this section on hardware because all of the major test-sets will meet your needs and you should be more concerned with the interface.

Protection Relay Test-Set Current Amplifiers

Here’s a quick summary of the current amplifier specifications from the major test-set manufacturers’ specification sheets in alphabetical order:

Doble F6150SV Manta MTS-5100 Omicron CMC 356
3-Phase Max Current 35 A (70 A*) 60 A* 64 A
3-Phase Max VA 175 VA (262.5 VA*) 900 VA* 860 VA
3-Phase Current (V) 70 V peak 50 V rms
6-Phase Max Current 17.5 A (35 A*) 30 A* 32 A
6-Phase Max VA 87.5 VA (131.25 VA*) 450 VA* 430 VA
6-Phase Max Current (V) 70 V peak 35 V peak
1-Phase Max Current 105 A (210 A*) 180 A* 128 A
1-Phase Max VA 525 VA (787.5 VA*) 2400 VA* 1740 VA
1-Phase Max Current (V) 70 V peak 140 V Peak

* Indicates the specification is not continuous.

What do these specs mean to you?

Current Amplifier Magnitude

All of these test-sets can generate roughly the same amount of current, but the Omicron can generate that current for longer periods of time.  This shouldn’t matter much during standard protection relay testing because protective relays should operate faster at higher currents. If you need more current than shown in the specifications, all of the manufacturers have amplifier units to generate additional current channels, and Manta allows users to control any two MTS-5×00 test-sets from one control panel.

Some relays, like pilot-wire relays, require current in the milliamp range. You want to have those relays ready to test during the demonstration. If your favorite test-set fails this test, ask the manufacturer if they have a work-around and see if it is acceptable to you.

Current Amplifier VA

The VA specification indicates how much energy each channel can produce. All of these test-sets have no problem testing any digital relay, but many electromechanical relays require more energy to operate because the applied current energizes coils and moves parts inside the relay. A lower VA specification means that you may have to physically change wiring between tests to create a signal that has more VA. A higher VA means fewer wiring changes between tests, which is obviously more convenient.

If you plan on testing a lot of electromechanical relays, you may want to give the MTS-5100 and CMC 356 bonus points on your evaluation.

Current Amplifier Compliance Voltage

The VA specification is a bit misleading because there are some electromechanical relays that don’t really require more VA, they require a larger voltage behind the current to “push” the current into the relay.  The specification “current (V)” from the table is the maximum compliance voltage that can push the current in that configuration. You should be careful when reviewing this specification because it is often missing, or it’s rated in different voltage references.  You don’t want to compare peak voltages to rms voltages because they aren’t the same thing. RMS voltages are 70.7% of peak voltages, so make sure you compare apples to apples.

The MTS-5100 has the largest per phase compliance voltage, which means fewer wiring changes between tests. But the CMC 356 single-phase specification is higher, so there are a few relays that the CMC 356 will be able to test that the MTS-5100 cannot.

The F6150 does not list the compliance voltage in its specification, but we can guess that it is lower than the other two test-sets because the VA is significantly lower. The F6150 has convertible voltage channels, so if one of the relays you plan on testing requires more than 140Vpeak or 99Vrms, you may want to give the Doble bonus points as long as that test requires less than 9.0A, and you are willing to change leads more often between tests on other, probably more common, relays.

Collect your highest burden relays and make sure you test the worst of them during the product demonstration, and you test them all during the evaluation period. Here is a list of electromechanical relays with high burdens to start your search.

  • ABB/Westinghouse IRD-9
  • ABB/Westinghouse CO-7
  • ABB/Westinghouse CA
  • GE IRQ

Reliability and Customer Support

Hardware reliability and customer support can be very important issues that can be difficult to judge until you are a customer. I don’t think anyone would argue that the CMC 356 is the most reliable test-set, and I would give it extra points on the reliability front.

There is no possible way that you could learn, and retain, all of the functionality built into any test-set model, so there must be good documentation and technical support available when you have questions. We’ll talk more about technical support in the evaluation section below.

Protection Relay Test-Set Voltage Amplifiers

Here’s a quick summary of the main voltage amplifier specifications:

Doble F6150SV Manta MTS-5100 Omicron CMC 356
4-Phase Max Voltage 300 V* 250 V 300 V
4-Phase Max VA 75 VA 85 VA 75 VA
1-Phase Max Voltage 600 V 750 V 600 V
1-Phase Max VA 300 VA 250 VA 275 VA
DC Voltage 6 – 300VDC 10 – 350 VDC 0 – 264 VDC
DC Voltage Watts 90 W 150 W 50 W

* 6-voltage channels are available

What do these specs mean to you?

All of the test-sets can provide a power supply for a relay, and supply three-phase voltages up to the specifications listed above. If you require more than 250V three-phase, then bonus points to the F6150 and CMC 356.

The F6150 can power a relay and supply six voltages simultaneously, and the CMC 356 can power the relay with four dedicated voltages. The MTS-5100’s fourth voltage channel allows the user to have three AC/DC voltages and a relay power supply, or 4 AC voltages. All of these test-sets can test six-phase voltage balance relays, but the MTS-5100 and CMC 356 require slightly more complicated wiring connections to do so.

If you plan on testing electromechanical reclosing relays, be sure to try and test them during the demonstration or evaluation period, because the motors in these relays require more VA than any other relay. If a test-set isn’t powerful enough to test your reclosing relays but you love the interface, it’s not the end of the world.  You can build an inexpensive, and simple, power supply that plugs into the wall for those troublesome relays.

If you have GE UR relays and plan on bench testing them, make sure your test-set can supply the inrush current needed to get them energized. Again, finding an alternate power supply would be a good idea if your favorite test-set fails this test, because it shouldn’t be a reason to strike a test-set off the list of prospects.

Protective Relay Test-Set Interface

Once you’ve selected the test-sets that meet your minimum hardware requirements, it’s time to call in the manufacturers for a demonstration. Be sure to have the relays listed in the hardware section ready to test at the demonstration, along with a couple of the most common relays that you test. Tell the representative what relays you will have at the demonstration and provide settings if they ask, so that they will be prepared to show you everything you need to know. Also ask them how much time they will need to give their presentation, along with some hands-on time so that your relay testers can play with the interface on your sample relays to get a feel for the workflow with an expert in the room. How prepared they are when they come for the demonstration should give you a good first impression about the quality of care you can expect when you are a customer.

When they arrive, be sure to remind them that you want to see some relays being tested, and not just a presentation. The representative should ask you about your current test procedures, what kinds of relays and tests you perform, and what problems you are specifically trying to solve by purchasing a new set. Let them know this information if they don’t ask so that they can tailor the presentation to you.

The test-set interface is where everything becomes subjective. If the hardware doesn’t meet your needs, it’s easy to eliminate that test-set from the running. All of the major test-sets have different strengths and weaknesses, and I’ll give my opinions here. You and I may come from different backgrounds, so it is more important for you and your technicians to get your hands on a test-set in the evaluation period to see if the software is the right fit for your goals and temperaments.

Manual Control

All test-sets have some kind of control panel that gives you complete control over the test parameters, the ability to save manual test plans, and some have the ability to save your results.

Omicron Test Universe

Quick CMC has a lot of possibilities and is extremely powerful. However, more options almost always means more complexity and it can take quite a while to get used to the interface.  Most of the options are hidden in pull-down lists or alternate screens, which cuts into productivity.  You can control every aspect of the test manually on a channel-by-channel basis, or you can use some of the intelligence in the software to assist you by doing some of the calculations and configurations for you. You can do more in this control screen compared to its competitors, but it often takes you longer to do simple tasks.

You can also order a front-panel interface for the CMC 356 that is quite functional with some very useful features. However, the screen is small and the menu order/button placement can limit productivity.

This test-set usually appeals to a relay tester with an engineering mindset who prefers to use a mouse and keyboard, and trusts the software to help them when it is appropriate.

Doble Protection Suite

The Control Panel tab has many features designed for productivity, but it provides very little help for new users. Relay testers must manually calculate all magnitudes and test angles.  A “Phase Rotate” button makes life easier after the first test is entered, but that initial setup is completely dependent on the relay tester. The fine and coarse controls are excellent for pickup tests, but there is no Prefault function, which can make impedance testing tedious without disabling the LOP setting.  The location and setup of sources, inputs and outputs, and timers are a little inconvenient which makes timing tests slightly more difficult compared to the competitors.

Doble does not have any meaningful front-panel interface.

This test-set tends to appeal to relay testers who like to “figure it out themselves” and are comfortable using spreadsheets and databases.

Manta Test Systems

The MTS-5100 controls are designed to be operated via its front-panel interface with no PC required for testing. The primary focus of the software is productivity, and all button positions and functionality have that goal in mind. The controls are designed around the three most common fault types, and the test-set automatically reconfigures the amplifiers for those fault types to minimize setting changes and increase productivity. Parts of the screen can be customized to show electrical calculations (such as watts, impedance, reactance, sequence components), timers, and other operating characteristics. There are also preset modes (impedance, synchronizing, and differential relays, etc.) that allow you to see the operating characteristics as you manually test. The fault-based functionality, front-panel interface, and flexibility can require a different mind-set compared to the competition that takes some getting used to.

Manta does have PC software to control the MTS-5100, but it is a copy of the front-panel interface, which makes software control of the test-set similar to playing a game on a PC that was designed for tablets and arcades.

This test-set appeals to relay testers who understand the power system and like to be involved in the physical aspect of testing by pressing buttons and turning dials.

Automated Control

All test-sets have some form of automation where a relay tester inputs some settings and the test-set performs a series of tests using pre-configured test procedures.

Manta Test Systems

The MTS-5100 has several “Productivity Modes” that the user can use to automatically or manually test specific elements inside a relay. The relay tester selects a productivity mode, enters the relay or system settings, defines some test characteristics, and runs a test. The procedure is repeated for all elements and zones inside the relay. Most productivity modes use the same fault-type philosophy from the manual test controls, so all elements can be tested without changing settings.  You can often use the equipment nameplate data or relay settings when configuring a test, so there are fewer translation errors between the relay and test-set settings. The test values are always shown on the screen and manual control is also available in most modes, so troubleshooting can be significantly easier than their competitors.

All channels can be ramped independently in the manual test menu to test elements not available in the productivity modes and users are able to directly control the channel harmonics to simplify harmonic testing.

Omicron Test Universe

Omicron has many Test Modules that cover just about the entire gamut of relay testing. Every mode is extremely powerful and this is where the Omicron software shines. You can define all zones, or levels, of a protection element on one screen so you can see how all of the different protection zones, or levels, interact. You can also select test-points visually in most test modules where you simply click wherever you want to add a test point, and the software configures everything it needs to test those points. You can also add multiple tests at once and, most impressively, the test-set will also perform no-go tests to document that the relay will not operate when outside of the protective zone. However, it can be difficult to troubleshoot these tests when something goes wrong because the actual current and voltages injected into the relay are not shown in real time, and/or are not available in the test plan setup.

The Test Modules are typically universal modes with European-style labels, so an engineering background is very useful when determining the correct characteristic to use. (For example, do you use kL, RE/RL and Xe/XL, or Z0/Z1 when testing an SEL ground distance impedance element?)

Doble Protection Suite

The Doble Protection Suite offers macros for automated testing that are based on electromechanical relay test procedures. The software allows you to select the type of test (voltage, current, impedance, etc.), the kind of test (single point, multi point, ramp, etc.), and then the relay tester defines every parameter of the test manually.  Like the MTS-5100, all elements and zones are individual tests that stand alone. Like the Omicron Test Universe, you are sometimes expected to know what formula the relay uses to calculate its characteristic (V/[I*[1+K]] or [V/[K*I]] for example). The test-set has macros for every conceivable combination of tests, but it does take some getting used to. Troubleshooting is difficult, and we have found in classes that it can be difficult to test elements like line impedance without changing settings because of the automated test characteristics.

Test Routine and Reports

All of the test-sets have some form of reporting feature that allows you to save and report your test results, but how they organize test routines for future tests is quite different.

Doble Protection Suite

The Doble Protection Suite allows you to save your test procedure as a single file that contains a series of Test Plans. The Test File is organized by tabs where you can enter the:

  • Nameplate data
  • List of Test Plans
  • System Nominal Values
  • Protection Settings (relay settings)
  • Worksheet of calculations
  • Attachments (other documents like coordination study or relay manual)
  • Notes

The software has a database foundation, so spreadsheet and database users will find the interface familiar. The software shines at allowing variables into test plans based on settings or worksheet values. You can cut and paste from spreadsheets directly into test plans, and import parameters from external files.

The default reports are database driven and have limited formatting options. The database foundation of the reports would make them easier to import into an external reporting system for NERC/FERC purposes.

This test system is good for organizations that test the same relays and configurations repeatedly, and have relay test technicians that have the time and skills to create their own custom test plans.

Manta Test Systems

The MTS-5100 stores every individual test as a separate file. You can save a series of tests in a directory and open each file, one at a time, to complete a relay test routine. Each test can contain the Relay Nameplate, Location, Expected Results, and limited Notes, or it can be configured as a template where the report will inherit data from previous tests. Because of Manta’s focus on actual testing productivity, you can often test a series of relays manually via the front-panel faster than it takes the competition to create a test plan for one relay, but the ability to create a test procedure that others can, or must, follow is a missing component of their test system. Some kind of external system is required to make sure all of the tests are completed on each relay.

Every test report can be saved in html or xml format.  Html files can be opened by any device that can open a webpage, so it is a universal format that requires no special software.  Xml files can be imported into Manta’s RapidReporter software that organizes the test by relay and test procedure. RapidReporter can provide limited NERC/FERC reporting and has a report editor that allows relay testers the most flexibility when creating reports.  All reports are text based.

On its own, this test system is good for organizations like testing companies who test different relays and configurations on a regular basis.  It is also good for organizations who have a small relay inventory and long intervals between tests where it may not make economic sense to spend a lot of time creating a repeatable, automated test plan that may be obsolete in one or two test periods.

Omicron Test Universe

Omicron Test Universe embeds individual tests into a dynamic document that also serves as the report. You can create a test object with all of relay information and settings, and then mix and match all of the available Test Modules into one document. You can write directly on the document between tests, or cut and paste nearly any picture or text from another program directly into the report, which makes it easy to customize the report look and feel for your organization and document metering tests. Everything is stored in one document, so it is easy to see the entire test process, and you can add pauses and instructions between each test. You can also link the test plans into the RIO system and import relay settings to make dynamic test plans that change based on the relay settings, but that functionality is easier with Doble’s Protection Suite.

The report and test plan are the same thing, which can have some benefits. Most of the test modules can also plot graphs and phasor diagrams, so the final report can look more inviting than the typical text-based report. There are limited formatting options for each module, so a perfectionist could spend a long time formatting a report to their specifications. The report is also stored in a proprietary format, which makes for larger than normal file sizes and is incompatible with any external reporting system for NERC/FERC outside of Omicron’s ADMO system (Maintenance management solution for protection systems).

Enoserv /RTS Software

The RTS software package changed the landscape of relay testing by allowing organizations to use the same test routines across multiple test-set platforms. The software treats each test routine as a software program to offer version control and security that customizes the amount of flexibility relay testers have when testing. All tests and test routines are recorded with special attention towards reporting and document control that allows managers to manage their relay inventory, test intervals, and test results for NERC/FERC reporting. The default reports are text based with simple graphics.

Cross-platform control is a great idea but, unfortunately, it means that the pre-canned test procedures supplied with the software must work when using the least sophisticated test-set models supported; which makes for very simplistic test routines designed for electromechanical relays.  A comprehensive digital relay test routine should require much more sophisticated tests, which is possible with simple modifications to the existing test plans.  It is possible to use the software to create a comprehensive test plan for any relay with a good understanding of relay testing, the power system, and some BASIC programming skills.

Troubleshooting Enoserv/RTS plans is difficult with the F6150 and CMC 356 because there is no easy way to tell whether the problem is with the program, the interface between the software and test-set, or the relay. Troubleshooting typically involves repeating the test over and over again while using external metering and monitoring devices to find the problem.  Switching to manual is difficult because you must try and recreate the test plan in some kind of control panel, which adds an additional failure point.  Did you enter the test plan correctly?

Troubleshooting Enoserv/RTS is relatively simple with an MTS-5100. RTS re-programs the MTS-5100 between each test, and the MTS-5100 screen displays the voltages and currents in real-time when the test is running. If a test fails, you can stop the test and immediately perform the same test manually with identical parameters via the MTS-5100 front-panel. This allows you to quickly narrow down where the problem is for easier troubleshooting. The RTS/MTS-5100 is a powerful combination when used to their full potential.

Protective Relay Test-Set Evaluation

If the test-set representative was able to test your most troublesome relays during the demonstration, and you liked what you saw when they were testing the most common relays, ask them for an evaluation demo unit so that you and your relay testers can try it out in the wild. You’re making a major investment into a very specialized piece of equipment that you will probably standardize on for future purchases, so they should be willing to let you kick the tires for a couple of days. It’s a bad sign if they aren’t willing to let you try it out. Be sure to let them know that you realize you haven’t been trained properly and you don’t expect perfection, you just want to see if the equipment is user-friendly enough to do some basic testing.  You also shouldn’t expect to have an evaluation unit for more than a couple of days unless you plan on purchasing more than five test-sets.

Once you get your demo unit, check out the shipping case and accessories and see how they all fit together. Ask if soft-cases, or other case options, are available if you don’t like the existing case.

Check out the leads and find out what leads are included with the test-set if you purchase it.  Also find out if you can purchase a replacement set in the future.  Your leads will wear out before the test-set does.

Install the software, if any, on the same laptop you would be using in the field and make sure that your IT department hasn’t laid a trap that prevents the software from working on your laptop. Connect to the test-set and make sure there are no problems there.

Make a list of the most common relays and elements you test in your system and get a spare relay and some settings from your system. Load the settings into the relay and try to perform a pickup and trip test on each element using the instructions from the manual or any introduction videos the manufacturer may have.

Call the customer support line with a real question you found while testing, or make up a question based on one of the challenges you found when trying to figure something out about the test-set.  Were they responsive and did they seem knowledgeable about the test-set AND relay testing in general?

Protective Relay Test-Set Quotation

Once you’ve looked at the hardware, evaluated the interface, and kicked the tires, you probably have a favorite, or are torn between two different models. It is time to get a quotation from your two favorite test-set manufacturers. All the manufacturers have completely different products and pricing philosophies, so make sure you are comparing apples to apples with the following checklist (ignore the entries that don’t apply to your organization):

Test-Set #1 Test-Set #2
Base Price
Extra Current Channels
Extra Voltage Channels
Extra Accuracy
Basic Software
Advanced Software
Relay Test Plans
License Renewal Fees
Service Packages
Test Leads
Hard-Shell Shipping case
Soft-Shell Shipping Case
GPS Equipment
IRIG Interface
Current Amplifier
Wifi Enabled
Transducer Interface

So, What Is the Best Protective Relay Test-set?

It depends. Everything is a trade-off, but here’s a simple chart based on your basic testing requirements and personality.


You can get some more information about the test-sets here:

Manta Test Systems


About the Author Chris Werstiuk

Chris is an Electrical Engineering Technologist, a Journeyman Power System Electrician, and a Professional Engineer. He is also the Author of The Relay Testing Handbook series and founder of Valence Electrical Training Services. You can find out more about Chris here.

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